1. Field of the Invention
This invention relates to a blade which controls the quantity of a developer used to develop and render visible an electrostatic latent image formed on an image-bearing member (i.e., a developer quantity control blade), and a developing assembly to which this blade is attached. This invention also relates to a process for manufacturing the developer quantity control blade.
2. Related Background Art
FIG. 5 schematically illustrates the construction of a developing assembly. A one-component developer (also called a toner) 46 for example, held in a developer container 42, is pressed against, and to stick to, a developer-carrying member (also called a developing sleeve or developing roller) 43 by means of an elastic roller 45 which rotates in the direction of an arrow c. Thereafter, as the developer-carrying member 43 is rotated in the direction of an arrow b, the developer is carried from the developer container to an electrophotographic photosensitive member 41 which rotates in the direction of an arrow a. In such a mechanism, a blade member 47 of a developer quantity control blade 44 is kept in control with the developer-carrying member 43, and the quantity of the developer carried from the developer container to the developer-carrying member is controlled (regulated), where a thin layer of the developer is formed and at the same time the developer is provided with stated triboelectric charges (also called triboelectricity) at a contact zone.
The developer quantity control blade is commonly formed of a rubber plate, a metallic sheet, a resin plate or a laminate of any of these. The developer quantity control blade is made up from a blade member which is brought into pressure contact with the developer-carrying member and a support member which supports the blade member at a preset position. The face of the blade member that is brought into pressure contact with the developer-carrying member has a function of controlling the triboelectric charges of the developer. Accordingly, this face is also called a charge control face. The surface layer of this charge control face is also called a charge control layer in some cases.
As blade members used for negative-type toners, plate members of urethane rubbers, urethane resins or polyamide elastomers are used, for example. Also, as developer quantity control blades used for positive-type toners, those obtained by laminating a charge-providing layer of charge-controlled silicone rubber or the like to a metallic sheet are used.
With regard to a non-magnetic toner used in the formation of color images, its thin layer must be formed on a developing sleeve or a developing roller, providing the toner with high triboelectric charges, because the toner itself does not have any magnetic properties. In this case, as materials used in the charge control layer, they may include urethane rubbers, polyamide resins, polyamide elastomers, silicone rubbers and silicone resins. The charge control face is finished so as to have good face precision.
In recent years, fine-particle toners are used in developing assemblies having been made high-quality and full-color in which an electrophotographic process is applied, and hence the toners are required to be more uniformly pressed against, and made to stick to, the developing sleeve or developing roller. Especially because of any influence by the surface roughness of the charge control face, faulty images such as uneven images and undesirable lines may occur.
In recent years, fine-particle toners are used in developing assemblies having been made high-quality and full-color in which an electrophotographic process is applied, and hence the toners are required to be more uniformly pressed against, and made stick to, the developing sleeve or developing roller. Especially because of any influence by the surface roughness of the charge control face, faulty images such as uneven images and undesirable lines may occur.
Japanese Patent Application Laid-open No. 09-050185 discloses a proposal of a blade member made of a polyamide elastomer or a polyamide resin, used for negative-type toners. As a manufacturing method, a method making use of a metal mold having a mirror face is disclosed. Also, in blade members made of urethane rubbers, an example is reported in which the charge control face is similarly formed by mold face transfer. However, where the method disclosed in this publication is employed, the surface properties of the charge control face is influenced by how the mold mirror face is maintained and controlled, and there is a possibility of resulting in non-uniform product quality depending on how it has been controlled.
In respect of positive-type toners also, how the mold mirror face is maintained and controlled is also an important quality control item in developer quantity control blade members made of thermosetting silicone rubbers or urethane rubbers.
However, although the developer has been transported under control using such a developer quantity control blade manufactured under severe product quality control in the manner as stated above, a difficulty as stated below has arisen in some cases.
That is, where the developer quantity control blade is kept in pressure contact with the developer-carrying member at a pressure-contact pressure necessary for charging the developer sufficiently and for forming a uniform thin layer, this has caused an imperceptible deformation in the developer-carrying member in some cases. Especially when the developing assembly is stopped from being driven and is left as it is, the developer-carrying member undergoes deformation. Even though the deformation is imperceptible, it has come about in some cases that the developer-carrying member does not recover from its deformation after it is resumed being driven. Then, this deformation has caused faulty images such as lines and uneven images in some cases.
On the other hand, if the developer-carrying member is made to have a high surface hardness in order to keep the developer-carrying member from its deformation, it has come about in some cases that the developer quantity control blade wears soon, that the blade can not provide the developer with the stated triboelectricity or that the developer-carrying member can not transport the developer in the stated quantity.
Thus, it has been unable to well keep the developer-carrying member from undergoing such imperceptible deformation, and the developer-carrying member's deformation taken place while the developing assembly is stopped has caused faulty images such as lines and uneven images in some cases.